Antenna Splitter

[Mike F.]

Besides the 3dB loss, is there any reason I cannot use a single Comant XPDR/DME antenna and a high-quality 2-way splitter/combiner to feed both antenna inputs on the Skyradar D2? Even with the 3dB loss, I'm thinking an externally-mounted antenna would be better than the stock antennas inside the aircraft.

[rdassow]

I'm not speaking on any authority other than I have background in RF theory.

I would say the splitter would be fine for the 978MHz spectrum but may be problematic in the new 1090MHz spectrum. I'm not sure how you could determine if this is actually the case when you test it since both frequency spectrums right now work similar BUT my understanding is that 978 is to be phased out over time. 978 will only be used in the rare case you don't have a groundstation and are interrogating airplane-to-airplane.

I could be wrong.

rdassow from techpilotz
 

[SkyRADARSupport]

There is no reason you can not use splitter if you can live with 3db loss. It works fine with splitter and wideband antenna.

Regards!

Besides the 3dB loss, is there any reason I cannot use a single Comant XPDR/DME antenna and a high-quality 2-way splitter/combiner to feed both antenna inputs on the Skyradar D2? Even with the 3dB loss, I'm thinking an externally-mounted antenna would be better than the stock antennas inside the aircraft.

[SkyRADARSupport]

I think you are  mistaken about 978 MHz, it uses much better modulation and overall better designed for further expansion than 1090 MHz. It also carries weather and other information which is not available on 1090 MHz.

I'm not speaking on any authority other than I have background in RF theory.

I would say the splitter would be fine for the 978MHz spectrum but may be problematic in the new 1090MHz spectrum. I'm not sure how you could determine if this is actually the case when you test it since both frequency spectrums right now work similar BUT my understanding is that 978 is to be phased out over time. 978 will only be used in the rare case you don't have a groundstation and are interrogating airplane-to-airplane.

I could be wrong.

rdassow from techpilotz

[rdassow]

SkyRADARSupport,

I would love to know if you can verify this for certain as I am a ground instructor (U.S.A/FAA) and we're being told that 1090 is going to be 'the standard' for the US airspace system, and 978 is going to be 'the standard' outside the US airspace system.

Essentially I am being told: 1090 is how you are going to receive information from ground stations, such as displaying last minute TFR's, Nexrad, etc. 978 is going to be AIRCRAFT-TO-AIRCRAFT communication for traffic awareness outside the U.S. where ground station 1090 won't be available.

Please correct me if I am misunderstanding this, as the FSDO's don't seem to have a lot of answers.......

ryan from techpilotz

[SkyRADARSupport]

978 MHz is used only in USA at the moment, i'm not aware of any other country using 978 or planning to use it. Weather and TFRs/NOTAMs/etc transmitted only on 978 MHz.

1090 MHz is international standard and in USA it is used only for traffic/TCAS/Transponder signals.

Both 978 and 1090 support aircraft-to-aircraft as well as ground up-link. Although ground up-link information on 1090 MHz is limited to TIS-B traffic only.

SkyRADARSupport,

I would love to know if you can verify this for certain as I am a ground instructor (U.S.A/FAA) and we're being told that 1090 is going to be 'the standard' for the US airspace system, and 978 is going to be 'the standard' outside the US airspace system.

Essentially I am being told: 1090 is how you are going to receive information from ground stations, such as displaying last minute TFR's, Nexrad, etc. 978 is going to be AIRCRAFT-TO-AIRCRAFT communication for traffic awareness outside the U.S. where ground station 1090 won't be available.

Please correct me if I am misunderstanding this, as the FSDO's don't seem to have a lot of answers.......

ryan from techpilotz